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jober
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max intrfaces on Router Boards

Wed Aug 04, 2004 12:04 am

I would like to know what the maximum number of wireless cards one SHOULD use on a RouterBoard AP?
I am using 6 at this time and I think I may need to move 3 of the wireless cards over to another RouterBoard.
2 prism 200mw .11B cards and 4 atheros ABG cards in .11A mode.
Any input would be graet.
 
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lastguru
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Wed Aug 04, 2004 1:58 am

What do you mean by maximal number? What do you experience with 6 cards: powering issues or performance issues?
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jober
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BOTH

Wed Aug 04, 2004 3:36 am

BOTH
1: I had xi-1000 zcomax radios before and I saw speeds of 2 to 4.5 megs and with the new MT ap I am getting 512k to 2 megs. With -59db I would think the speed would be much better.
I have ran the bandwidth test from the clients and it show tx 3.5 megs.

We're using one radio for a ptp to the NOC and one for a ptp to another tower and two radios are AP in B the last two AP in A(All on a single routerboard)

2: Yes we do have power problems. The MT is rebooted every 8 to 12 hours with watch dog because it stops working. We would drive out to the tower and the thing would not respond so POWER OFF and back on and up it comes.
We buy a backup AP and it looks like we are going to replace the one up there the backup AP to see if it's a hardware glich.

Sorry if I'm not clear, another day with out food
 
tully
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Wed Aug 04, 2004 9:36 am

The PCMCIA 200mW card use allot of power. The RouterBOARD has 15W of power at 5V. The base config uses about 4.5W. So, you are hitting the max with six cards (and there are power losses going from 5V to 3.3V).

John
 
jober
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Will this Help

Wed Aug 04, 2004 9:48 pm

Tully
I have a coax cable running up to the same place the MT is so I could run power thru it and plug into the power jack on the board if that would help. As of now the power is running thru the POE ethernet port with 320 feet of Outdoor Cat5e cable.
 
tully
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Thu Aug 05, 2004 8:05 am

The 15W is the internal power system on the board. If you are using external POE, then you need to write which POE injector you are using. This could be the problem.

John
 
jober
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PoE

Fri Aug 06, 2004 5:26 am

Its the 3Com PoE that Eje sales at wisp-router. It's the 3Com mfm# 3CNJPSE. It looks to be 48volts
 
tully
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Fri Aug 06, 2004 8:05 am

With that many interfaces, you may have exceeded the power supply. I can't say for sure. I will think if we should test this -- we don't sell a 3com power supply.

John
 
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Fri Aug 06, 2004 1:28 pm

The 3com POE injector is an 802.3af compliant unit. It provides 400ma @ 48vdc. If my math is correct, that should be 19.2 watts.

http://www.3com.com/products/en_US/deta ... e=purchase
 
tully
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Fri Aug 06, 2004 1:38 pm

You have to consider that you have a 320 ft run of cable that is losing some power. Also, our power supply is somthing like 90% efficient from 48V to 5V (which is very good) -- but it means that you lose 10% there (turned into heat). The RB14 has a linear power converter that loses about 20% going from 5V to 3.3V for the mpci. So, you may need more than 19.2W. We initially sold 24W power supplies and now we sell 30W power supplies as they run cooler and will be able to supply our RB300 also.

Another potential problem is power spikes in the long POE run. If the Ehternet is mounted next to the grouding rod or a power line going up a tower, then it could get problems from those lines. If it is in a building, then it shouldn't be a problem as there is so much metal criss crossing in modering building and that grounds everthing.

We have an expert on this that is doing some design work on our newer power supplies and we will try to get him to write a paper about this subject. Analog power design is extremely complex -- it is something artwork to get something perfect.

John
 
jober
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I'll take one PLEASE!

Sun Aug 08, 2004 2:28 am

I looked for the 30W power supply, but I did not see it on your site. Can you post a link to it?

Thanks once more for your infinite wisdom. :lol:
 
tully
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Sun Aug 08, 2004 10:37 am

http://www.routerboard.com/parts.html#poe52

It has a 30W power supply and 25W can be put out at the POE injector.

I am not sure that it is in stock as there were some design problems.

The RB53 may have more power than your 3Com, though we need to test it.

John
 
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Sun Aug 08, 2004 10:11 pm

tully, can you give us some more info about RB300
 
tully
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Sun Aug 08, 2004 11:01 pm

A prototype should be ready in six weeks and then full production if it works correction.

John

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